The improvement of wireless access performance is urgently needed due to a recent sharp increase in data traffic. It is considered to overlay and dispose macrocells, which use relatively low frequencies in the ultra-high frequency (UHF) band, and small cells, which use relatively high frequencies, in order to build a high-speed and large-capacity wireless access network. Full-dimension (FD) multi-input multi-output (MIMO), which compensates for high propagation losses, is considered for small cells, which use high frequency bands. FD-MIMO is a technique of two-dimensionally disposing base station antennas in the horizontal and vertical directions for MIMO communication.
Patent Literature 1 discloses a technique of allowing a terminal to select a desired weighting factor from weighting factor candidates (codebook) and feed back the desired weighting factor to a base station to flexibly decide the weighting factor of a system that uses multiple antennas.